nir/lower_gs_intrinsics: Return progress if append_set_vertex_and_primitive_count makes progress

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Fixes: 542d40d698 ("nir: Add new GS intrinsics that maintain a count of emitted vertices.")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12802>

src/compiler/nir/nir_lower_gs_intrinsics.c

@@ -302,6 +302,7 @@ append_set_vertex_and_primitive_count(nir_block *end_block, struct state *state)
          }
 
          nir_set_vertex_and_primitive_count(b, vtx_cnt, prim_cnt, stream);
+         state->progress = true;
       }
    }
 }